1. Field of the Invention
The present invention relates to an adhesive label sheet and a manufacturing method thereof, and more particularly, to an adhesive label sheet which can be attached to articles to be produced through a high temperature firing furnace or to be subjected to indirect heat treatment at high temperature, and a manufacturing method thereof.
2. Description of Related Art
Conventionally, when attaching identification labels to articles such as ceramics, electronic substrates, or cathode ray tubes which must pass through a firing furnace or an electric furnace in the manufacturing process, these identification labels should be attached to articles cooled after the high temperature furnace process since they are likely to melt away or burn at high temperature. Using this method, however, it is difficult to recognize information on the articles before the furnace process. Accordingly, these conventional labels are not sufficient for identification labels such as bar-code labels.
The conventional identification label includes a substrate layer having good release properties, an adhesive layer and an ink-receiving layer. These labels are attached to articles by an adhesive force of the adhesive layer while the substrate layer is separated by an automatic process. Thus, if the adhesive layer melts or deforms, it is difficult for the bar-code to be recognized. The adhesive layer, as an important constituent of the label sheet, should be stable at high-temperatures, i.e., in a firing furnace, and adhere firmly to the articles.
A related prior art bar-code label based on ceramics is disclosed in U.S. Pat. No. 4,775,786. In accordance with the teaching of that patent, the material used in the label is fragile during the drying process due to a lack of flexibility, and requires a lengthy drying time and is costly.
Further, a pattern formation sheet and a manufacturing method thereof are disclosed in U.S. Pat. No. 4,971,858. In that patent, the ink-receiving layer of the sheet includes a glass frit in addition to a metal powder, a metal oxide powder and an organic binder. The fused glass frit may be attached to an article or the bar-code which may be damaged due to air bubbles generated by the glass frit. Further, the label manufacturing process is complicated and the manufacturing cost is also high.
Also, European Patent No. 0 649 126 Al discloses a label which includes a film composed of a silicone resin, an inorganic monocrystalline fiber and an adhesive wherein the adhesive is made of a silicone resin and metal powder. However, the adhesive is not stable at high temperatures and the adhesiveness thereof is not desirable.